It will be appreciated that nuclear fuel assemblies must be dependable in order to allow reliable operation of nuclear reactors. Thus, design and construction provisions for such assemblies have been drawn up.
These provisions impose a general framework and minimum criteria which the assembly constructors must take into consideration.
As far as the helical damping spring is concerned, the design provisions require verification by means of tests that the integrity of the spring has not been affected during the impact brought about in the event of a shutdown of the reactor.
Although the criterion imposed by the design provisions allows assemblies to be designed with satisfactory reliability, it would be desirable to limit the safety margins during design in order to reduce the mass and the cost of the assemblies constructed.